/*
 * Copyright (c) 2000, 2008, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package javax.swing;

import java.util.*;
import javax.swing.event.*;
import java.io.Serializable;


/**
 * This class provides the ChangeListener part of the
 * SpinnerModel interface that should be suitable for most concrete SpinnerModel
 * implementations.  Subclasses must provide an implementation of the
 * <code>setValue</code>, <code>getValue</code>, <code>getNextValue</code> and
 * <code>getPreviousValue</code> methods.
 *
 * @author Hans Muller
 * @see JSpinner
 * @see SpinnerModel
 * @see SpinnerListModel
 * @see SpinnerNumberModel
 * @see SpinnerDateModel
 * @since 1.4
 */
public abstract class AbstractSpinnerModel implements SpinnerModel, Serializable {

  /**
   * Only one ChangeEvent is needed per model instance since the
   * event's only (read-only) state is the source property.  The source
   * of events generated here is always "this".
   */
  private transient ChangeEvent changeEvent = null;


  /**
   * The list of ChangeListeners for this model.  Subclasses may
   * store their own listeners here.
   */
  protected EventListenerList listenerList = new EventListenerList();


  /**
   * Adds a ChangeListener to the model's listener list.  The
   * ChangeListeners must be notified when the models value changes.
   *
   * @param l the ChangeListener to add
   * @see #removeChangeListener
   * @see SpinnerModel#addChangeListener
   */
  public void addChangeListener(ChangeListener l) {
    listenerList.add(ChangeListener.class, l);
  }


  /**
   * Removes a ChangeListener from the model's listener list.
   *
   * @param l the ChangeListener to remove
   * @see #addChangeListener
   * @see SpinnerModel#removeChangeListener
   */
  public void removeChangeListener(ChangeListener l) {
    listenerList.remove(ChangeListener.class, l);
  }


  /**
   * Returns an array of all the <code>ChangeListener</code>s added
   * to this AbstractSpinnerModel with addChangeListener().
   *
   * @return all of the <code>ChangeListener</code>s added or an empty array if no listeners have
   * been added
   * @since 1.4
   */
  public ChangeListener[] getChangeListeners() {
    return listenerList.getListeners(ChangeListener.class);
  }


  /**
   * Run each ChangeListeners stateChanged() method.
   *
   * @see #setValue
   * @see EventListenerList
   */
  protected void fireStateChanged() {
    Object[] listeners = listenerList.getListenerList();
    for (int i = listeners.length - 2; i >= 0; i -= 2) {
      if (listeners[i] == ChangeListener.class) {
        if (changeEvent == null) {
          changeEvent = new ChangeEvent(this);
        }
        ((ChangeListener) listeners[i + 1]).stateChanged(changeEvent);
      }
    }
  }


  /**
   * Return an array of all the listeners of the given type that
   * were added to this model.  For example to find all of the
   * ChangeListeners added to this model:
   * <pre>
   * myAbstractSpinnerModel.getListeners(ChangeListener.class);
   * </pre>
   *
   * @param listenerType the type of listeners to return, e.g. ChangeListener.class
   * @return all of the objects receiving <em>listenerType</em> notifications from this model
   */
  public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
    return listenerList.getListeners(listenerType);
  }
}
